docs: def timelines(fig, y, xstart, xstop, color='b'):
      """Plot timelines at y from xstart to xstop with given color."""
      fig.hlines(y, xstart, xstop, color, lw=4)
      fig.vlines(xstart, y+0.03, y-0.03, color, lw=2)
      fig.vlines(xstop, y+0.03, y-0.03, color, lw=2)